1. Field of the Invention
This invention relates to an adsorptively acting silicatic complexing agent for alkaline earth metal ions as well as a method of producing the same. This invention is particularly concerned with such an adsorptively acting silicating complexing agent which not only has a high surface area and is characterized by a number of micropores, but also has a high ion exchange capacity. p 2. Discussion of the Prior Art
It is known that clay minerals of the montmorillonite-beidellite series are natural cation exchangers and as such are capable of binding alkaline earth ions and heavy metal ions. For example, natural bentonite has an ion exchange capacity of about 80 to 100 mval per 100 grams. The ion exchange is based on an electronegative excess charge on the stratified silicate montmorillonite, the chief component of the bentonites. By the natural isomorphic replacement of, for example, trivalent aluminum ions in the octahedral layer with bivalent, usually magnesium ions, or also of tetravalent silicon ions with trivalent aluminum ions, for example, in the tetrahedral layer, an electropositive deficit of charge results in the silicate laminae which is compensated by the binding of, for example, alkali ions or alkaline earth ions.
In the case of acid activated minerals from the montmorillonite-beidellite series, ions are dissolved out of the octahedral layer, the amount of the octahedral layer ions entering into solution and of the tetrahedral layer ions which are soluble in acid being able to vary, depending on the acid concentration, temperature, time and pressure. The specific surface area and the number of micropores increases, while the ion exchange capacity decreases.
In many applications, however, it is desirable for the good adsorption capacity provided in the high specific surface area to be combined with a good ion exchange capacity. This is generally the case whenever, in addition to the binding of cations, a binding or adsorption is desired of molecules which may be unpolar or polar to a greater or lesser degree. This involves, for example, dye molecules, colored polymerization products, protein substances, and impurities in fats and oils.
Other applications are waste waters containing fats, oils and other chemicals such as proteins, phenols, solvent residues, etc., in addition to cationic impurities. Similar problems are encountered in the laundry industry, where the alkaline earth ions contained as hardness formers in the wash water must be removed as well as the dirt and the particles of coloring matter and fats.